This invention relates to electrochromic elements and more particularly electrochromic elements which are useful as light controllable windows for buildings, automobiles and passenger vehicles and various types of light controllable glasses to be used for indoor decoration or partitions; display devices; and antidazzle mirrors for automobiles and other vehicles.
A conventional electrochromic device such as a light controllable glass of conventional type as disclosed in Japanese Patent Laid-Open Publication No. 63-18336 is known which glass comprises a chromogenic material in the form of a film obtained by sputtering or vacuum-depositing an inorganic oxide such as tungsten oxide (WO3) over a transparent electrically conductive film.
However, the conventional film formation techniques must be carried out under vacuum, resulting in increased production costs and a requirement of a large size vacuum apparatus if an electrochromic element of a large area is intended to be produced. Furthermore, since a substrate is heated at an elevated temperature during sputtering, it is necessary to select certain conditions if a substrate other than a glass, such as a synthetic resin-made substrate is used, resulting in difficulties in reducing the weight of an electrochromic element.
There is also a problem that tungsten oxide can only make an electrochromic element exhibit blue color.
An object of the present invention is to provide an electrochromic element which can be manufactured using an inexpensive color developing material with easy operations and can easily be changed in color tone.
An electrochromic device proposed by the present invention solves the above-mentioned problems of the prior art by forming an ion conductive material layer containing a specified electrochromic material.
Namely, according to the present invention, there is provided an electrochromic element comprising two conductive substrates, at least one of which is transparent, and an ion conductive layer disposed therebetween and containing an electrochromic substance comprising a compound represented by formula (1) below or a derivative thereof, formula (1) being represented by the formula 
wherein R1, R2, R3, R4 and R5 are each independently hydrogen or a hydrocarbon residue having from 1 to 20 carbon atoms and may be the same or different, Ar1 and Ar2 are each independently a divalent aromatic hydrocarbon residue and may be the same or different and a is an integer of greater than 0.
It is preferred that the ion conductive material layer further contains a compound having a viologen structure represented by the formula 
wherein Xxe2x88x92 and Yxe2x88x92 may be the same or different and are each a counter anion selected from the group consisting of a halogen anion, Cl4xe2x88x92, BF4xe2x88x92, PF6xe2x88x92, CH3COOxe2x88x92 and CH3(C6H4)SO3xe2x88x92.
In the present invention, two electrically conductive substrates, at least one of which is transparent, are used. The term xe2x80x9celectrically conductive substratexe2x80x9d designates substrates which have a function as an electrode. Therefore, the conductive substrates used in the invention encompass those entirely formed from an electrically conductive material or formed with a non-electrically conductive substrate and an electrode layer disposed thereon. Regardless of whether a substrate is electrically conductive or not, it necessarily has a smooth surface at normal temperature but may have a flat or curved surface and may be deformable under stress.
At least of one of the two electrically conductive substrates is a transparent electrically conductive substrate and the other may be a transparent or opaque or reflective electrically conductive substrate.
Two conductive substrates both of which are transparent are suitable for a display device and a light controllable glass. A combination of a transparent conductive substrate and an opaque conductive substrate is suitable for a display device, while a combination of a transparent conductive substrate and a reflective substrate is suitable for an electrochromic mirror.
The transparent conductive substrate is generally formed by laminating a transparent electrode layer over a transparent substrate. The term xe2x80x9ctransparencyxe2x80x9d used herein designates an optical transmission ranging from 10 to 100 percent.
The opaque conductive substrate is may be a laminate obtained by laminating an electrode layer over one surface of a metal plate or a non-conductive opaque substrate such as various opaque plastics, ceramics, glasses, woods and stones.
The reflective electrically conductive substrate may be exemplified by (1) a laminate comprising a non-conductive transparent or opaque substrate and a reflective electrode layer formed thereon, (2) a laminate comprising a no-conductive transparent substrate having a transparent electrode layer on one of its surfaces and a reflective electrode layer on the other surface, (3) a laminate comprising a non-conductive transparent substrate having a reflective layer formed thereon and further a transparent electrode layer formed thereon, (4) a laminate comprising a reflective substrate and a transparent electrode layer formed thereon and (5) a plate-like substrate which itself functions as a reflective layer and an electrode.
No particular limitations is imposed on the transparent substrate which may thus be a color or colorless glass, a reinforced glass and a resin of color or colorless transparency. Specific examples of such a resin include polyethylene terephthalate, polyamide, polysulfone, polyether sulfone, polyether etherketone, polyphenylene sulfide, polycarbonate, polyimide, polymethyl methacrylate and polystyrene.
The substrates used in the present invention must have a smooth surface at normal temperature.
There is no particular restriction to the transparent electrode layer as long as it meets the requirements for achieving the purpose of the present invention. Specific examples of the electrode layer include electrically conductive film such as thin films of metals such as gold, silver, chrome, copper and tungsten or metal oxides such as ITO (In2O3xe2x80x94SnO2), tin oxide, silver oxide, zinc oxide and vanadium oxide.
The electrode has a film thickness in the range of usually 100 to 5,000 and preferably 500 to 3,000 angstrom. The surface resistance of the electrode is usually in the range of 0.5-500 and preferably 1-50 xcexa9/sq.
No particular limitation is imposed on a method of forming the electrode layer. Any suitable conventional methods may be employed, depending upon the metal and metal oxide constituting the electrode. In general, the formation of the electrode layer is carried out by vacuum evaporation, ion plating, sputtering and a sol-gel method. The thickness of the electrode layer is selected within the range such that the transparency thereof is not affected. The electrode layer may be partially provided with an opaque electrode-activator for the purpose of imparting oxidation-reduction capability, electric conductivity and electric double layer capacitance, the electrode-activator being provided in an amount such that the transparency of the entire electrode layer is not harmed. Electrode activators eligible for the purpose of the invention are a metal such as copper, silver, gold, platinum, iron, tungsten, titanium and lithium, an organic material having oxidation-reduction capability such as polyaniline, polythiophen, polypyrrole and phthalocyanine, a carbon material such as active carbon and graphite and a metal oxide such as V2O5, MnO2, NiO and Ir2O3 and mixtures thereof. A variety of resins may be used for integrating the electrode activator in the electrode. The opaque electrode activator may applied onto an electrode by forming on an ITO transparent electrode a composition comprising an active carbon fiber, graphite and an acrylic resin into a micro pattern in the shape of stripes or by forming on a thin-film of gold a composition comprising V2O5, acetylene black and butyl rubber in the shape of a mesh.
No particular limitation is imposed on the reflective electrode layer as long as it is stable electrochemically and has a specular surface. Eligible for the reflective electrode layer includes the films of metal such as gold, platinum, tungsten, tantalum, rhenium, osmium, iridium, silver, nickel and palladium and the film of an alloy such as platinum-palladium, platinum-rhodium and stainless steel. The reflective electrode layer is necessarily disposed onto a substrate or a transparent substrate with the reflectiveness and specularity of the layer maintained. The reflective electrode layer is formed onto a substrate by any suitable conventional method such as vacuum deposition, ion-plating and sputtering.
No particular limitation is imposed on a substrate on which the reflective electrode layer is disposed. The substrate may be transparent or opaque. Specific examples of the substrate include those as exemplified with respect to the transparent substrate described above, a variety of plastics, resins, glasses, woods and stones.
No particular limitation is imposed on materials for the above-mentioned reflective plate or layer as long as it can provide a specular surface. For example, silver, chrome, aluminum and stainless steel are eligible.
The plate-like substrate having a reflective layer and functioning as an electrode may be exemplified by the substrates exemplified with respect to the reflective electrode among which are self-supportive.
The ion conductive material layer to be disposed between the two conductive substrates is now described.
The ion conductive substance layer used in the present invention is composed of an ion conductive substance containing a specified electrochromic substance.
In the present invention, the term xe2x80x9cion conductive substancexe2x80x9d designates a substance having an ion conductivity of 1xc3x9710xe2x88x927S/cm or more at room temperature and playing a role of coloring, decoloring or discoloring an electrochromic substance. No particular limitation is imposed on the ion conductive material, which may thus be liquid, gel or solid. Solid ion conductive materials are particularly preferred for the purpose of the invention so as to be able to obtain an electrochromic mirror which is overall solid and excelled in various performances for practical usage.
Liquid Ion Conductive Material
Eligible liquid ion conductive materials are those dissolving a supporting electrolyte such as salts, acids and alkalis in a solvent.
Although any suitable solvents may be used as long as they can dissolve a supporting electrolyte, preferred are those having polarity. Specific example of such solvents are water and an organic polar solvent such as methanol, ethanol, propylene carbonate, ethylene carbonate, dimethylsulfoxide, dimethoxyethane, acetonitrile, xcex3-butyrolactone, xcex3-valerolactone, sulforan, dimethylformamide, dimethoxyethane, tetrahydrofuran, propionnitrile, glutaronitrile, adiponitrile, methoxyacetonitrile, dimethylacetoamide, methylpyrrolidinone, dimethylsulfoxide, dioxolane, trimethylphosphate and polyethylene glycol. Preferred are propylene carbonate, ethylene carbonate, dimethylsulfoxide, dimethoxyethane, acetonitrile, xcex3-butyrolactone, sulforan, dioxolane, dimethylformamide, tetrahydrofuran, adiponitrile, methoxyacetonitile, dimethylacetoamide, methylpyrrolidinone, dimethylsulfoxide, trimethylphosphate and polyethylene glycol. These may be used singlely or in combination.
Although not restricted, salts used as a supporting electrolyte may be alkali metal salts, inorganic ion salts such as alkaline earth metal salts, quaternary ammonium salts and cyclic quaternary ammonium salts. Specific examples of such salts include alkali metal salts of lithium, sodium or potassium such as LiClO4, LiSCN, LiBF4, LiAsF6, LICF3, SO3, LiPF6, LiI, NaI, NaSCN, NaClO4, NaBF4, NaAsF6, KSCN and KCl, quaternary ammonium salts or cyclic quaternary ammonium salts such as (CH3)4NBF4, (C2H5)4NBF4, (n-C4H9)4NBF4, (C2H5)4NBr, (C2H5)4NClO4 and (n-C4H9)4NClO4 and mixtures thereof.
Acids used as a supporting electrolyte may be exemplified by inorganic acids and organic acids, specific examples of which include sulfuric acid, hydrochloric acid, phosphoric acid, sulfonic acid carboxylic acid.
Alkalis used as a supporting electrolyte include sodium hydroxide, potassium hydroxide and lithium hydroxide.
Gelatinized-liquid Ion Conductive Material
The gelatinized-liquid ion conductive material may be those which are gelatinized or made to be viscous by adding a polymer or a gelatinizer to the above-mentioned liquid ion conductive material.
No particular limitation is imposed on the polymers, which thus may be polyacrylonitrile, carboxymethylcellulose, polyvinyl chloride, polyethylene oxide, polyurethane, polyacrylate, polyamide, polyacrylamide, cellulose, polyester, polypropyleneoxide and nation.
Preferred examples of the gelatinizers are oxyethylenemethacrylate, oxyethyleneacrylate, urethaneacrylate, acrylamide and agar-agar.
Solid Ion Conductive Material
No particular limitation is imposed on the solid ion conductive material as long as it is solid at room temperature and ion conductive. Preferred examples of such solid ion conductive materials are polyethyleneoxide, the polymer of oxyethylenemethacrylate, nafion, polystylene sulfonate, Li3N, Na-xcex2-Al2O3 and Sn(HPO4)2H2O. Particularly preferred are polymer solid electrolytes obtained by polymerizing a polyethyleneoxide-based compound, an oxyalkyleneacrylate-based compound or a urethaneacrylate-based compound.
First examples of such polymer solid electrolytes are those obtained by solidifying a composition (hereinafter referred to as Composition A) containing the above-described organic polar solvent and supporting electrolyte and a urethaneacrylate of the formula (3) below.
The term xe2x80x9ccurexe2x80x9d used with respect to the polymer solid electrolyte as well as Composition B hereinafter described designates a state where a polymerizing or crosslinking component is cured with the progress of polymerization (polycondensation) or crosslinking and thus the composition does not flow at room temperature. The composition thus cured has the basic structure in the form of network.
Formula (3) is represented by the formula 
wherein R6 and R7 may be the same or different and are each a group of formula (4), (5) or (6) below, R8 and R9 may be the same or different and are each a C1-C20, preferably C2-C12 divalent hydrocarbon residue, Y is selected from a polyether unit, a polyester unit, a polycarbonate unit and the mixed unit thereof and b is an integer from 1 to 100, preferably 1 to 50 and more preferably 1 to 20. Formulae (4), (5) and (6) are represented by the formulae 
wherein R10, R11 and R12 may be the same or different and are each a hydrogen atom or a C1-C3 alkyl group and R13 is a C1-C20, preferably C2-C8 organic residue of divalent through quatervalent.
Specific examples of such organic residues are a hydrocarbon residue such as alkyltolyl, alkyltetratolyl and alkylene of the formula 
wherein R14 is a C1-C3 alkyl group or hydrogen, p is an integer from 0 to 6 and if c is 2 or greater, R14 groups may be the same or different.
The hydrocarbon residue may be a group part of which hydrogen atoms are substituted by an oxygen-containing hydrocarbon group such as a C1-C6, preferably C1-C3 alkoxy group and a C6-C12 aryloxy group.
Specific examples of R13 group in formulae (4) thorough (6) are those represented by the following formulae: 
Each of the divalent hydrocarbon residues represented by R8 and R9 in formula (3) is exemplified by a divalent chain-like hydrocarbon group, an aromatic hydrocarbon group and an alicyclic-containing hydrocarbon group. Specific examples of the chain-like divalent hydrocarbon group are those represented by formula (7) above.
Specific examples of the aromatic hydrocarbon group and alicyclic-containing hydrocarbon group are those represented by the following formulae: 
wherein R15 and R16 may be the same or different and each are a phenylene group, a phenylene group having an alkyl subsutituent, a cycloalkylene group and a cycloalkylene group having an alkyl subsutituent, R17, R13, R19 and R20 may be the same or different and each are a hydrogen atom or a C1-C3 alkyl group.
Specific examples of the groups R8 and R9 in formula (3) are those represented by the following formulae: 
In formula (3), xe2x80x9cYxe2x80x9d indicates a polyether unit, a polyester unit, a polycarbonate unit and mixed unit thereof. Each of these units is represented by the following formulae: 
In formulae (a) through (d), R21 through R26 may be the same or different and are each a C1-C20, preferably C2-C12 divalent hydrocarbon residue. Preferred for R24 are C2-C6 divalent hydrocarbon residues. Preferred for R21 through R26 are straight or branched alkylene groups among which methylene, ethylene, trimethylene, tetramethylene, pentamethylene, hexamethylene and propylene groups are preferred for R23, and ethylene and propylene groups are preferred for R21, R22 and R24 through R26. The letter xe2x80x9cexe2x80x9d in formula (a) is an integer from 2 to 300, preferably 10 to 200, the letter xe2x80x9cfxe2x80x9d is an integer from 1 to 300, preferably 2 to 200, the letter xe2x80x9cgxe2x80x9d is an integer from 1 to 200, preferably 2 to 100, the letter xe2x80x9chxe2x80x9d is an integer from 1 to 200, preferably 2 to 100 and the letter xe2x80x9cixe2x80x9d is an integer from 1 to 300, preferably 10 to 200.
Each unit represented by formulae (a) through (d) may be a copolymer of the same or different units. Namely, if a plurality of R21 through R26 are present, the groups of each R21 thorough R26 may be the same or different. Preferred examples of the above-mentioned polymer are polymers of ethyleneoxide and propyleneoxide.
The urethaneacrylate may be prepared by any suitable conventional method. Urethaneacrylate of formula (3) has a molecular weight in the range from 2,500 to 30,000, preferably 3,000 to 20,000. The urethaneacrylate has preferably 2-6, more preferably 2-4 polymerization functional groups per molecule.
An organic polar solvent (organic nonaqueous solvent) is added in an amount of 100-200, preferably 200-900 weight parts per 100 parts of the urethaneacrylate. The addition of the organic polar solvent in a too less amount would result in insufficient ion conductivity, while the addition of the organic polar solvent in a too much amount would cause reduced mechanical strength. The supporting electrolyte may be salts, acids or alkalis. The supporting electrolyte should be added in an amount of 0.1 to 30, preferably 1 to 20 weight percent of the organic polar solvent.
Composition (A) is obtained by solidifying the above-described essential components, namely, urethaneacrylate, organic nonaqueous solvent and supporting electrolyte. If necessary, any suitable optional components may be added to Composition (A) as long as they are not obstructive to the achievement of the purpose of the invention. Such components may be crosslinkers and photo- or thermal polymerization initiators.
Second examples of the polymeric solid electrolyte are polymeric solid electrolytes obtained by solidifying a composition (hereinafter referred to as Composition (B)) comprising an organic polar solvent, a supporting electrolyte, a monofunctional acryloyle-modified polyalkylene oxide of formula (18) below or a polyfunctional acryloyle-modified polyalkylene oxide of formula (19) or (20) below.
Formula (18) is represented by the formula 
wherein R27, R28, R29 and R30 may be the same or different and are each hydrogen and an alkyl group having from 1 to 5 carbon atoms and j is an integer of 1 or greater. Specific examples of the alkyl group include methyl, ethyl, i-propyl, n-propyl, n-butyl, t-butyl and n-pentyl. Preferred for R22, R23 and R34 are hydrogen and a methyl group. Preferred for R30 are hydrogen and methyl and ethyl groups.
The letter xe2x80x9cjxe2x80x9d in formula (18) is an integer of 1 or greater, usually from 1 to 100, preferably from 2 to 50 and more preferably from 2 to 30.
Specific examples of compounds represented by formula (18) are those having 1-100, preferably 2-50 and more preferably 1-20 oxyalkylene units, such as methoxypolyethylene glycol methacrylate, methoxypolypropylene glycol methacrylate, ethoxypolyethylene glycol methacrylate, ethoxypolypiropylene glycol methacrylate, methoxypolyethylene glycol acrylate, methoxypolypropylene glycol acrylate, ethoxypolyethylene glycol acrylate, ethoxypolypropylene glycol acrylate and mixtures thereof.
If xe2x80x9cjxe2x80x9d is 2 or greater, the compound may be those having different oxyalkylene units, that is, copolymerized oxyalkylene units which for instance have 1-50, preferably 1-20 oxyethylene units and 1-50, preferably 1-20 oxypropylene units. Specific examples of such compounds are (ethylene.propylene) glycol methacrylate, ethoxypoly (ethylene.propylene) glycol methacrylate, methoxypoly (ethylene.propylene) glycol methacrylate, methoxypoly (ethylene.propylene) glycol acrylate, ethoxypoly methoxypoly (ethylene.propylene) glycol acrylate and mixtures thereof.
The polyfunctional acryloyl-modified polyalkylene oxide may be a bifunctional acryloyl-modified polyalkylene oxide represented by the formula 
wherein R31, R32, R33 and R34 are each hydrogen and a C1-C5 alkyl group and k is an integer of 1 or greater; or a polyfunctional acryloyl-modified polyalkylene oxide having more than three functional groups represented by the formula 
wherein R35, R36 and R37 are each hydrogen and a C1-C5 alkyl group, 1 is an integer of 1 or greater, m is an integer from 2 to 4 and L is a connecting group of valence indicated by m.
In formula (19), R31, R32, R33 and R34 are each hydrogen or a C1-C5 alkyl group, such as methyl, ethyl, i-propyl, n-propyl, n-butyl, t-butyl, t-butyl and n-pentyl among which preferred are hydrogen and particularly preferred is methyl.
The letter xe2x80x9ckxe2x80x9d in formula (19) is an integer of 1 or greater, usually from 1 to 100, preferably from 2 to 50, more preferably from 2 to 30. Preferred examples of compounds of formula (19) are those having 1-100, preferably 2-50, more preferably 1-20 oxyalkylene units such as polyethylene glycol diacrylate, polypropylene glycol dimethacrylate, polyethylene glycol diacrylate, polypropylene glycol dimethacrylate and mixtures thereof.
If k is 2 or greater, the compounds of formula (19) may be those having different oxyalkylene units, that is, polymerized oxyalkylene unit having 1-50, preferably 1-20 oxyethylene units and 1-50, preferably 1-20 oxypropylene units, such as poly(ethylene.propylene)glycol dimethacrylate, poly(ethylene.propylene)glycol diacrylate and mixtures thereof.
In formula (20), R35, R36 and R37 are each hydrogen or a C1-C5 alkyl group, such as methyl, ethyl, i-propyl, n-propyl, n-butyl, t-butyl and n-pentyl. Particularly preferred for R35, R36 and R37 are hydrogen and a methyl group.
The letter xe2x80x9clxe2x80x9d is an integer of 1 or greater, usually from 1 to 100, preferably from 2 to 50 and more preferably from 2 to 30.
The letter xe2x80x9cmxe2x80x9d indicates the number of connecting group xe2x80x9cLxe2x80x9d and is an integer from 2 to 4.
Connecting group xe2x80x9cLxe2x80x9d is a divalent, trivalent or quatravalent hydrocarbon group having 1-30, preferably 1-20 carbon atoms.
Such divalent hydrocarbon groups may be alkylene, arylene, arylalkylene, alkylarylene and hydrocarbon groups having those groups as the base skeleton. Specific examples of such hydrocarbon groups are those represented by the following formulae 
Such trivalent hydrocarbon groups may be alkyltryl, aryltryl, arylalkyltryl, alkylaryltryl and hydrocarbon groups having those groups as the base skeleton. Specific examples of such hydrocarbon groups are those represented by the following formulae: 
Such quatravalent hydrocarbon groups may be alkyltetraryl, aryltetraryl, arylalkyltetraryl, alkylaryltetraryl and hydrocarbon groups having those groups as the base skeleton. Specific examples of such hydrocarbon groups are those represented by the following formulae: 
Specific examples of compounds of formula (20) are those having 1-100, preferably 2-50, more preferably 1-20 of an oxyalkylene units such as
trimethylolpropanetri(polyethylene glycol methaacrylate),
trimethylolpropanetri(polyethylene glycol methaacrylate),
trimethylolpropanetri(polypropylene glycol acrylate),
trimethylolpropanetri(polypropylene glycol methaacrylate),
tetramethylolmethanetetra(polyethylene glycol acrylate),
tetramethylolmethanetetra(polyethylene glycol methaacrylate),
tetramethylolmethanetetra(polypropylene glycol acrylate),
tetramethylolmethanetetra(polypropylene glycol methaacrylate),
2,2-bis[4-(acryloxypolyethoxy)phenyl]propane,
2,2-bis[4-(methaacryloxypolyethoxy)phenyl]propane,
2,2-bis[4-(acryloxypolyisopropoxy)phenyl]propane,
2,2-bis[4-(methaacryloxypolyisopropoxy)phenyl]propane and mixtures thereof.
If l is 2 or greater, compounds of formula (20) may be those having different oxyalkylene units, that is, polymerized oxyalkylene units having 1-50, preferably 1-20 of oxyethylene units and 1-50, preferably 1-20 oxypropylene units. Specific examples of such compounds include trimethylolpropanetri(poly(ethylene.propylene)glycol acrylate), trimethylolpropanetri(poly(ethylene.propylene)glycol methaacrylate), tetramethylolmethanetetra(poly(ethylene.propylene)glycol acrylate), tetramethylolmethanetetra(poly(ethylene.propylene) glycol acrylate) and mixtures thereof.
There may be used the difunctional acryloyl-modified polyalkyleneoxide of formula (19) and the polyfunctional acryloyl-modified polyalkyleneoxide of formula (20) in combination. When these compounds are used in combination, the weight ratio of the compound of formula (19) to that of formula (20) is in the range from 0.01/99.9 to 99.9/0.01, preferably from 1/99 to 99/1 and more preferably from 20/80 to 80/20.
The above-described organic polar solvent should be added in an amount of 50-800, preferably 100-500 weight percent based on the weight of the polyfunctional acryloyl-modified polyalkyleneoxide. The above-described supporting electrolyte should be added in an amount of 1-30, preferably 3-20 weight percent based on the total weight of the polyfunctional acryloyl-modified polyalkyleneoxide and the organic polar solvent.
Similarly to Composition (A), if necessary, cross-linkers or polymerization initiators may be added to Composition (B). Such components should be added in an amount of 0.005-5, preferably 0.01-3 weight percent based on the total weight of the polyfunctional acryloyl-modified polyalkylene oxide.
In the present invention, regardless of whether the ion conductive substance is liquid, gelatinized liquid or solid, a specified electrochromic substance is dispersed therein and used for the formation of an ion conductive substance layer.
An electrochromic substance which is a requisite component in the present invention and is dispersed into the ion conductive substance, typically the above-described Compositions (A) or (B), is a compound represented by formula (1) below or a derivative thereof: 
In formula (1), R1, R2, R3, R4 and R5 are each independently hydrogen or a hydrocarbon residue having from 1 to 20, preferably 1 to 12 carbon atoms and may be the same of different. Specific examples of the hydrocarbon residue are an alkyl group such as methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl and n-hexyl groups, an alkoxyphenyl group such as methoxyphenyl and ethoxyphenyl groups, an alkylphenyl group such as tolyl and ethylphenyl groups, an aryl group such as phenyl group, an alkylaryl group and a derivative of these hydrocarbon residues.
In formula (1), Ar1 and Ar2 are each independently a divalent aromatic hydrocarbon residue having from 6 to 18 carbon atoms and may be the same or different. Specific examples are the following functional groups: 
wherein R1 is the same as that of formula (1).
Specific examples of the functional groups are as p-phenylene, m-phenylene, p-biphenylene, methyl-p-phenylene, ethyl-p-phenylene, methoxy-p-phenylene, methyl-m-phenylene, ethyl-m-phenylene and methoxy-m-phenylene and derivatives thereof, phenylene groups of formula (5), (6) or (7) or derivatives thereof, a divalent monocyclic or condensed polycyclic aromatic hydrocarbon residue such as 1,5- or 2,7-naphtylene, 1,4-, 1,5- or 2,6-anthraquinonylene, 2,4- or 2,7-fluorenonylene, byrenylene, 2,7-phenanethraquinonylene, 2,7-(9-dicyanomethylene)fluorenonylene, dibenzotrobonzyl, dicyanomethylenedibenzotrobonzyl and benzanthronylene groups; a divalent hetero atom-containing condensed heterocyclic aromatic hydrocarbon residue such as divalent heterocyclic groups exemplified by 2-phenylbenzooxazolexzyl, 2-phenylbenzimidazolezyl, carbazolezyl, 2-phenylbenzotriazolezyl, dibenzothiophenezyl, dibenzothiophenoxidezyl, 9-acridonzyl, xanthonezyl and phenoxanezyl groups.
In formula (1) the letter xe2x80x9caxe2x80x9d is an integer of 1 or greater, preferably from 0 to 10, more preferably from 0 to 5, further more preferably from 0 to 3.
Specific examples of a compound of formula (1) are
N,N,Nxe2x80x2,Nxe2x80x2-tetramethylbenzidine, N,N,Nxe2x80x2,Nxe2x80x2-tetraethylbenzidine,
N,N,Nxe2x80x2,Nxe2x80x2-tetraphenylbenzidine, N,N,Nxe2x80x2,Nxe2x80x2-tetrabenzylbenzidine,
N,N,Nxe2x80x2,Nxe2x80x2-tetrapropylbenzidine, N,N,Nxe2x80x2,Nxe2x80x2-tetrabutylbenzidine,
N,Nxe2x80x2-diphenyl-N,Nxe2x80x2-ditolylbenzidine, N,N,Nxe2x80x2,Nxe2x80x2-tetratolylbenzidine,
N,Nxe2x80x2-diphenyl-N,Nxe2x80x2-dimethylbenzidine,
N,Nxe2x80x2-diphenyl-N,Nxe2x80x2-diethylbenzidinee,
N,Nxe2x80x2-diphenyl-N,Nxe2x80x2-dipropylbenzidine,
N-methacrylicethyl-N,Nxe2x80x2,Nxe2x80x2-triethylbenzidine,
N-methacrylicethyl-N,Nxe2x80x2,Nxe2x80x2-trimethylbenzidine,
N-methacrylicmethyl-N,Nxe2x80x2,Nxe2x80x2-triethylbenzidine,
N-methacrylicmethyl-N,Nxe2x80x2,Nxe2x80x2-trimethylbenzidine,
N-methacrylicethyl-N,Nxe2x80x2,Nxe2x80x2-triphenylbenzidine,
N-methacrylicphenyl-N,Nxe2x80x2,Nxe2x80x2-trimethylbenzidine,
N-methacrylicphenyl-N,Nxe2x80x2,Nxe2x80x2-triethylbenzidine,
N-methacrylicphenyl-N,Nxe2x80x2,Nxe2x80x2-triphenylbenzidine,
N-methacrylicphenyl-Nxe2x80x2-phenyl-N,Nxe2x80x2-diitolylbenzidine,
N-acryliethyl-N,Nxe2x80x2,Nxe2x80x2-triethylbenzidine,
N-acryliethyl-N,Nxe2x80x2,Nxe2x80x2-trimethylbenzidine,
N-acrylicmethyl-N,Nxe2x80x2,Nxe2x80x2-triethylbenzidine,
N-acrylicethyl-N,Nxe2x80x2,Nxe2x80x2-trimethylbenzidine,
N-acrylicethyl-N,Nxe2x80x2,Nxe2x80x2-triphenylbenzidine,
N-acrylicphenyl-N,Nxe2x80x2,Nxe2x80x2-trimethylbenzidine,
N-acrylicphenyl-N,Nxe2x80x2,Nxe2x80x2-triethylbenzidine,
N-acrylicphenyl-N,Nxe2x80x2,Nxe2x80x2-triphenylbenzidine,
N-acrylicphenyl-Nxe2x80x2-phenyl-N,Nxe2x80x2-ditolylbenzidine,
N,N,Nxe2x80x2,Nxe2x80x2-tetraethylphenylenediamine,
N,N,Nxe2x80x2,Nxe2x80x2-tetraphenylphenylenediamine,
N,N,Nxe2x80x2,Nxe2x80x2-tetrabenzylphenylenediamine,
N,N,Nxe2x80x2,Nxe2x80x2-tetrapropylphenylenediamine,
N,N,Nxe2x80x2,Nxe2x80x2-tetrabutylphenylenediamine,
N,Nxe2x80x2-diphenyl-N,Nxe2x80x2-ditolylphenylenediamine,
N,N,Nxe2x80x2,Nxe2x80x2-tetratolylphenylenediamine,
N,Nxe2x80x2-diphenyl-N,Nxe2x80x2-dimethylphenylenediamine,
N,Nxe2x80x2-diphenyl-N,Nxe2x80x2-diethylphenylenediamine,
N,Nxe2x80x2-diphenyl-N,Nxe2x80x2-dipropylphenylenediamine,
N-methacrylicethyl-N,Nxe2x80x2,Nxe2x80x2-triethylphenylenediamine,
N-methacrylicethyl-N,Nxe2x80x2,Nxe2x80x2-trimethylphenylenediamine,
N-methacrylicmethyl-N,Nxe2x80x2,Nxe2x80x2-triethylphenylenediamine,
N-methacrylicmethyl-N,Nxe2x80x2,Nxe2x80x2-trimethylphenylenediamine,
N-methacrylicethyl-N,Nxe2x80x2,Nxe2x80x2-triphenylphenylenediamine,
N-methacrylicphenyl-N,Nxe2x80x2,Nxe2x80x2-trimethylphenylenediamine,
N-methacrylicphenyl-N,Nxe2x80x2,Nxe2x80x2-triethylphenylenediamine,
N-methacrylicphenyl-N,Nxe2x80x2,Nxe2x80x2-triphenylphenylenediamine,
N-methacrylicphenyl-Nxe2x80x2-phenyl-N,Nxe2x80x2-citolylphenylendiamine,
N-acrylicethyl-N,Nxe2x80x2,Nxe2x80x2-triethylphenylenediamine,
N-acrylicethyl-N,Nxe2x80x2,Nxe2x80x2-trimethylphenylenediamine,
N-acrylicmethyl-N,Nxe2x80x2,Nxe2x80x2-triethylphenylenediamine,
N-acrylicmethyl-N,Nxe2x80x2,Nxe2x80x2-trimethylphenylendiamine,
N-acrylicethyl-N,Nxe2x80x2,Nxe2x80x2-triphenylphenylenediamine,
N-acrylicphenyl-N,Nxe2x80x2,Nxe2x80x2-trimethylphenylenediamine,
N-acrylicphenyl-N,Nxe2x80x2,Nxe2x80x2-trimethylphenylenediamine,
N-acrylicphenyl-N,Nxe2x80x2,Nxe2x80x2-triphenylphenylenediamine and
N-acrylicphenyl-Nxe2x80x2-phenyl-N,Nxe2x80x2-ditolylphenylenediamine.
In the present invention, derivatives of a compound of formula (1) may be used together with or in place of a compound of formula (1). The term xe2x80x9cderivativexe2x80x9d denotes a polymer resulting from the polymerization of a compound of (1) through one or more of hydrocarbon residues of R1 through R5 or a compound in which a compound of formula (1) bonds to the ion conductive material.
Although not restricted, the concentration of a compound of formula (1) or a derivative thereof in the ion conductive layer is usually from 0.00001 to 50 percent by weight, from 0.0001 to 30 percent by weight and more preferably from 0.001 to 10 percent by weight. The weight ratio of a compound of formula (1) or a derivative thereof to the polyfunctional acryloyl-modified polyalkyleneoxide is usually from 1/0.001 to 1/1, preferably from 1/0.05 to 1/0.5.
Besides a compound of formula (1) or a derivative thereof, an electrochromic substance having a viologen structure represented by formula (2) below is preferably dispersed in the ion conductive material layer of the present invention: 
In formula (2), Xxe2x88x92 and Yxe2x88x92 are each a counter anion and may be the same or different and an anion selected from the group consisting of a halogen anion, ClO4xe2x88x92, BF4xe2x88x92, PF6xe2x88x92, CH3COOxe2x88x92 and CH3(C6H4)SO3xe2x88x92. The halogen anion may be Fxe2x88x92, Clxe2x88x92, Brxe2x88x92 and Ixe2x88x92.
No particular limitation is imposed on the electrochromic substance as long as it has a viologen structure and exhibits electrochromic properties. Therefore, the electrochromic substance may be high molecular weight compounds having a viologen structural unit of formula (2) or a unit containing the viologen structure as a repeating unit; compounds having at the terminal ends of a viologen structure high molecular weight substituents; or high molecular compounds having molecular chains part of which is substituted with a group having a viologen structure of formula (2).
The high molecular weight compounds having a unit containing the viologen structure of formula (2) as a repeating unit may be those of which side or main chain is formed by viologen structural units. No particular limitation is imposed on the repeating units forming the main chains of high molecular weight compounds. Therefore, such repeating units forming the main chain may be hydrocarbon units, oxygen-containing units, nitrogen-containing units, polysiloxane units and copolymerized units thereof.
Specific examples of a compound having a viologen structure of formula (2) are N,Nxe2x80x2-diheptylbipylidiniumdibromide,
N,Nxe2x80x2-diheptylbipyridiniumdichloride,
N,Nxe2x80x2-diheptylbipyridinium diperchlorate,
N,Nxe2x80x2-diheptylbipyridinium tetraphloroborate,
N,Nxe2x80x2-diheptylbipyridiniumhexaphlorophosphate,
N,Nxe2x80x2-dihexylbipyridiniumdibromide,N,Nxe2x80x2-dihexylbipyridiniumcdichloride,
N,Nxe2x80x2-dihexylbipyridiniumdiperchlorate,
N,Nxe2x80x2-dihexylbipyridiniumtetraphloroborate,
N,Nxe2x80x2-dihexylbipyridiniumdihexaphlorophosphate,
N,Nxe2x80x2-dipropylbipyridiniumdibromide,N,Nxe2x80x2-dipropylbipyridiniumdichloride,
N,Nxe2x80x2-dipropylbipyridiniumdiperchlorate,
N,Nxe2x80x2-dipropylbipynidiniumtetraphloroborate,
N,Nxe2x80x2-dipiropylbipyridiniumdihexaphlorophosphate,
N,Nxe2x80x2-dibenzylbipyridinium dibromide,
N,Nxe2x80x2-dibenzylbipyridiniumperchlorate,
N,Nxe2x80x2-dibenzylbipyridiniumtetraphloroborate,
N,Nxe2x80x2-dibenzylbipyridiniumdihexaphlorophosphate,
N,Nxe2x80x2-dimethacryloylethylbipyridinium dibromide,
N,Nxe2x80x2-dimethacryloylethylbipyridiniumdichlonide,
N,Nxe2x80x2-dimethacryloylethylbipyridiniumdiperchlorate,
N,Nxe2x80x2-dimethacryloylethylbipylidniumditetraphloroborate,
N,Nxe2x80x2-dimethacryloylethylbipyridiniumdihexaphlorophosphate,
N,Nxe2x80x2-diacryloylethylbipyridiniumdibromide,
N,Nxe2x80x2-diacryloylethylbipyridiniumdichloride,
N,Nxe2x80x2-diacryloylethylbipyridiniumdiperchlorate,
N,Nxe2x80x2-diacryloylethylbipyridiniumditetraphloroborate,
N,Nxe2x80x2-diacryloylethylbipyridiniumdihexaphlorophosphate,
N,Nxe2x80x2-dimethacryloylmethylbipyridiniumdibromide,
N,Nxe2x80x2-dimethacryloylmethylbipyridinium dichloride,
N,Nxe2x80x2-dimethacryloylmethylbipylidiniumdiperchlorate,
N,Nxe2x80x2-dimethacryloylmethylbipyridiniumditetraphloroborate,
N,Nxe2x80x2-dimethacryloylmethylbipyridiniumdihexaphlorophosphate,
N,Nxe2x80x2-diacryloylmethylbipyridiniumdibromide,
N,Nxe2x80x2-diacryloylmethylbipylldiniumdiperchlorate,
N,Nxe2x80x2-diacryloylmethylbipyridiniumditetraphloroborate,
N,Nxe2x80x2-diacryloylmethylbipyridiniumdihexaphlorophosphate,
N-heptyl-Nxe2x80x2-methacryloylethylbipyridiniumdibromide,
N-heptyl-Nxe2x80x2-methacryloylethylbipyridiniumdichlolide,
N-heptyl-Nxe2x80x2-methacryloylethylbipyridiniumdiperchlorate,
N-heptyl-Nxe2x80x2-methacryloylethylbipyridiniumditetraphloroborate,
N-heptyl-Nxe2x80x2-methacryloylethylbipyndiniumdihexaphlorophosphate,
N-heptyl-Nxe2x80x2-methacryloylethylbipyridiniumdibromide,
N-hexyl-Nxe2x80x2-methacryloylethylbipyridiniumdichloride,
N-hexyl-Nxe2x80x2-methacryloylethylbipyridiniumdiperchlorate,
N-hexyl-Nxe2x80x2-methacryloylethylbipyridiniumditetraphloroborate,
N-hexyl-Nxe2x80x2-methacryloylethylbipyridiniumdihexaphlorophosphate,
N-benzyl-Nxe2x80x2-methacryloylethylbipyridiniumdibromide,
N-benzyl-Nxe2x80x2-methacryloylethylbipyndiniumdichloride,
N-benzyl-Nxe2x80x2-methacryloylethylbipyridiniumdiperchlorate,
N-benzyl-Nxe2x80x2-methacryloylethylbipyridiniumditetraphloroborate,
N-benzyl-Nxe2x80x2-methacryloylethylbipyridiniumdihexaphrolophosphate,
N-butyl-Nxe2x80x2-methacryloylethylbipyridiniumdibromide,
N-butyl-Nxe2x80x2-methacryloylethylbipyridiniumdichloride,
N-butyl-Nxe2x80x2-methacryloylethylbipyridiniumdiperchlorate,
N-butyl-Nxe2x80x2-methacryloylethylbipyridiniumditetraphloroborate,
N-butyl-Nxe2x80x2-methacryloylethylbipyridiniumdihexaphrolophosphate,
N-propyl-Nxe2x80x2-methacryloylethylbipyridiniumdibromide,
N-propyl-Nxe2x80x2-methacryloylethylbipyridiniumdichloride,
N-propyl-Nxe2x80x2-methacryloylethylbipyridiniumdiperchlorate,
N-propyl-Nxe2x80x2-methacryloylethylbipyridiniumditetraphloroborate,
N-propyl-Nxe2x80x2-ethacryloylethylbipyridiniumdihexaphlorophosphate,
N-heptyl-Nxe2x80x2-methacryloylmethylbipyridiniumdibromide,
N-heptyl-Nxe2x80x2-methacryloylmethylbipyridiniumdichloride,
N-heptyl-Nxe2x80x2-methacryloylmethylbipynidiniumdiperchlorate,
N-heptyl-Nxe2x80x2-methacryloylmethylbipyridiniumditetraphloroborate,
N-heptyl-Nxe2x80x2-methacryloylmethylbipyridinumdiexaphlorophosphate,
N-heptyl-Nxe2x80x2-methacryloylmethylbipyridiniumdibromide,
N-hexyl-Nxe2x80x2-methacryloylmethylbipylidiniumdichloride,
N-hexyl-Nxe2x80x2-methacryloylmethylbipyriiliniumdtiperchlorate,
N-hexyl-Nxe2x80x2-methacryloylmethylbipyridiniumditetraphloroborate,
N-hexyl-Nxe2x80x2-methacryloylmethylbipyridiniumdihexaphlorophosphate,
N-benzyl-Nxe2x80x2-methacryloylmethylbipyridiniumdibromide,
N-benzyl-Nxe2x80x2-methacryloylmethylbipyridiniumdichloride,
N-benzyl-Nxe2x80x2-methacryloylmethylbipyridiniumdiperchlorate,
N-benzyl-Nxe2x80x2-methacryloylmethylbipyriditetraphroloborate,
N-benzyl-Nxe2x80x2-methacryloylmethylbipyridiniumdihexaphlorophosphate,
N-butyl-Nxe2x80x2-methacryloylmethylbipyridiniumdibromide,
N-butyl-Nxe2x80x2-methacryloylmethylbipyridiniumdichloride,
N-butyl-Nxe2x80x2-methacryloylmethylbipyridiniumdiperchlorate,
N-butyl-Nxe2x80x2-methacryloylmethylbipyridiniumditetraphloroborate,
N-butyl-Nxe2x80x2-methacryloylmethylbipyridiniumdihexaphlorophosphate,
N-propyl-Nxe2x80x2-methacryloylmethylbipyridiniumdibromide,
N-propyl-Nxe2x80x2-methacryloylmethylbipyridiniumdichloride,
N-propyl-Nxe2x80x2-methacryloylmethylbipyridiniumdiperchlorate,
N-propyl-Nxe2x80x2-methacryloylmethylbipyridiniumditetraphloroborate,
N-propyl-Nxe2x80x2-methacryloylmethylbipyridiniumdihexaphlorophosphate,
N-heptyl-Nxe2x80x2-methacryloylphenylbipyridiniumdibromide,
N-heptyl-Nxe2x80x2-methacryloylphenylbipyridiniumdichloride,
N-heptyl-Nxe2x80x2-methacryloylphenylbipyridiniumdiperchlorate,
N-heptyl-Nxe2x80x2-methacryloylphenylbipyridiniumditetraphloroborate,
N-heptyl-Nxe2x80x2-methacryloylphenylbipyridiniumdihexaphlorophosphate,
N-heptyl-Nxe2x80x2-methacryloylphenylbipyridiniumdibromide,
N-hexyl-Nxe2x80x2-methacryloylphenylbipyrdiniumdichloride,
N-hexyl-Nxe2x80x2-methacryloylphenylbipyridiniumdiperchlorate,
N-hexyl-Nxe2x80x2-methacryloylphenylbipyridiniumdihexaphlorophosphate,
N-hexyl-Nxe2x80x2-methacryloylphenylbipyridiniumdihexaphlorophosphate,
N-benzyl-Nxe2x80x2-methacryloylphenylbipyridiniumdibromnide,
N-benzyl-Nxe2x80x2-methacryloylphenylbipyridiniumdichloride,
N-benzyl-Nxe2x80x2-methacryloylphenylbipyridiniumdiperchlorate,
N-benzyl-Nxe2x80x2-methacryloylphenylbipyridiniumditetraphloroborate,
N-butyl-Nxe2x80x2-methacryloylphenylbipyridiniumdibromide,
N-butyl-Nxe2x80x2-methacryloylphenylbipyridiniumdichloride,
N-butyl-Nxe2x80x2-methacryloylphenylbipyridiniumdiperchlorate,
N-butyl-Nxe2x80x2-methacryloylphenylbipyridiniumditetraphloroborate,
N-butyl-Nxe2x80x2-methacryloylphenylbipyridiniumdihexaphlorophosphate,
N-propyl-Nxe2x80x2-methacryloylphenylbipyridiniumdibromide,
N-propyl-Nxe2x80x2-methacryloylphenylbipyridiniumdichloride,
N-propyl-Nxe2x80x2-methacryloylphenylbipyridiniumdiperchlorate,
N-propyl-Nxe2x80x2-methacryloylphenylbpyridiniumditetraphloroborate and
N-propyl-Nxe2x80x2-methacryloylphenylbipyridiniumidihexaphlorophosphate,
Another examples of a compound having a viologen structure are polymers or copolymers represented by the formula 
In formula (21), the letter xe2x80x9cpxe2x80x9d indicates an integer of 1 or greater, preferably from 1 to 1,000, and the letter xe2x80x9cqxe2x80x9d indicates an integer of 0 or greater, preferably from 0 to 1,000. R38 is a C1-C20, preferably C1-C12 divalent hydrocarbon residue or merely indicates the direct bond of the viologen group to a polymer chain not through the hydrocarbon residue, namely covalently bond. Specific examples of hydrocarbon groups include aliphatic hydrocarbon groups such as methylene, ethylene, propylene, tetramethylene, pentamethylene and hexamethylene and aromatic hydrocarbon groups such as phenylene, biphenylene and benzylidene. Specific examples of oxygen-containing hydrocarbon groups include aliphatic alkoxylene groups such as xe2x80x94OCH2xe2x80x94, xe2x80x94OCH2CH2xe2x80x94 and xe2x80x94OCH2CH2CH2xe2x80x94, aliphatic dialkoxylene groups such as xe2x80x94OCH2CH2Oxe2x80x94 and xe2x80x94OCH2CH2CH2Oxe2x80x94, aromatic aryloxy groups such as xe2x80x94O(C6H4)xe2x80x94 and xe2x80x94OCH2(C6H4)xe2x80x94 and aromatic diaryloxy groups such as xe2x80x94O(C6H4)O and xe2x80x94OCH2(C6H4)Oxe2x80x94.
Xxe2x88x92 and Yxe2x88x92 each indicate a counter anion which is a monovalent anion, with respect to viologen and may be the same or different. Xxe2x88x92 and Yxe2x88x92 may be a halogen anion such as Fxe2x88x92, Clxe2x88x92, Brxe2x88x92 and Ixe2x88x92, ClO4xe2x88x92, BF4xe2x88x92, PF6xe2x88x92, CH3COOxe2x88x92 and CH3(C6H4)SO6xe2x88x92.
R39, R40 and R41 are each a C1-C20, preferably C1-C12 hydrocarbon group and a hetero atom-containing subsutituent and a halogen atom. Preferred hydrocarbon groups for R39, R40 and R41 are alkyl groups such as methyl, ethyl, propyl and hexyl and an aryl group such as phenyl, tolyl, benzyl and naphtyl. Preferred hetero atom-containing substituents are a C1-C20, preferably C1-C12 oxygen-containing hydrocarbon group, amide, amino and cyano groups. Such oxygen-containing hydrocarbon groups include an alkoxyl group such as methoxy and ethoxy an aryloxy group such as phenoxy and triloxy, a carboxyl group and a residual carboxylic acid ester.
In the case where the compound of formula (21) is a copolymer, the copolymerization pattern of the repeating units may be that of block-, random- or alternate-copolymerization.
The viologen-structure compound may be copolymers or copolymers represented by the formula 
In formula (28), p, q and Xxe2x88x92 and Yxe2x88x92 are the same as defined in formula (21) and q is preferably 0. R42 and R44 may be the same or different and are each the same as those as defined with respect to R38 in formula (21) and R43 and R45 may be the same or different and each are the same as those as defined with respect to R39 in formula (21).
In the case where a compound of formula (22) is a copolymer, the copolymerization pattern of the repeating units may be that of block, random or alternate polymerization.
Moreover, the viologen structure compound may also be polymers or copolymers represented by the formula 
In formula (23), p, q and Xxe2x88x92 and Yxe2x88x92 are the same as those as defined in formula (21) and q is preferably 0. R46 is the same as those as defined with respect to R38 in formula (21) and R47, R48 and R49 may be the same or different and are each the same as those as defined with respect to R39 in formula (21).
In the case where the compound of formula (23) is a copolymer, the copolymerization pattern of the repeating units may be that of block, random or alternate of polymerization.
Furthermore, the compound having a viologen structure may be polymers represented by the formula 
In formula (24), t is an integer of 0 or greater, preferably from 0 to 20, u is an integer of 0-1,000 and R50 is the same as those as defined with respect to R38 in formula (21).
Further alternatively, the compound having a viologen structure may also be polymers or copolymers represented by the formula 
In formula (31), R is a C1-C10 alkyl group, v is an integer of 1 or greater, preferably from 1 to 1,000, R51 is the same as those as defined with respect to R38 in formula (21) and R52 is the same as those as defined with respect to R41 in formula (21).
Typical examples of the compound having a viologen structure used for the present invention have been exemplified by compounds of formulae (25) through (29). Specific examples of compounds which are included within the range of these formulae and which are not included within the range of these formulae but eligible for the invention are given below. xe2x80x9cPrxe2x80x9d in the following formulae indicates a propyl group and xe2x80x9cpxe2x80x9d and xe2x80x9cqxe2x80x9d are as defined in formula (21). 
The ion conductive substance contains the compound having a viologen structure in an amount from 0.00001 to 50 percent by weight, preferably 0.0001 to 30 percent by weight and more preferably 0.001 to 10 percent by weight. If necessary, an electrochromic compound of formula (1) or a compound having a viologen structure of formula (2) may be doped with a compound facilitating coloration.
The ion conductive substance layer of the electrochromic element according to the present invention is formed from an ion conductive substance contains requisitely an electrochromic substance composed of a compound of formula (1) or a derivative thereof, and if necessary may further contain a compound having a structure of formula (2).
Any suitable method can be employed for forming the ion conductive substance layer. When a liquid or gelatinized liquid ion conductive substance is used, the ion conductive substance containing an electrochromic substance dispersed therein is injected into the space provided between two electrically conductive substrates, i.e. counter conductive substrates, placed, facing each other and then sealed at the edges of the opposed surfaces, by vacuum injection, atmospheric injection or a meniscus method. Alternatively, when using a specific type of ion conductive substance, a method can be employed in which an ion conductive substance layer containing an electrochromic substance is formed on one of the electrically conductive substrates by sputtering, evaporation or a sol-gel method and the substrate is put together with the other substrate. Further alternatively, an electrochromic element according to the present invention can be obtained by inserting a film-like ion conductive substance containing an electrochromic substance between a pair of glasses to form a laminated glass.
When a solid ion conductive substance, particularly the above-described Composition A or B is used, a method can be employed in which the composition in an unsolidified state is inserted into the space between the counter conductive substrates with their peripheral edges being sealed, by vacuum injection, atmospheric injection or a meniscus method and is cured in a suitable manner.